Originally Posted by Boosted Performance

There are no shear pins, there is a key to hold the gear on to the shaft as it rotates. It is not possible for the key to come out with the cover on, and the gear in place. It is not a large key, so it just slides down the square hole on the right gear. You can pull that gear out to inspect it.

Those gears look mint.

Did you pull the gears out at all? If the motor is running there is absolutely no reason for a rebuild. I have never seen one of these fail.